In general, mayenite has hitherto been produced as, for example, a component of a protective layer for covering a dielectric layer of a plasma display panel (hereinafter referred to as “PDP”) by various methods.
The following Patent Document 1 discloses a production method of an oxide containing a mayenite type compound by using, as a raw material, a combination of a calcium compound and an aluminum compound or a compound containing calcium and aluminum and describes a production method of an oxide, which is characterized by including a step of mixing the above-described raw material to produce a mixture of the raw material and a step of heating and holding the mixed raw material in a reducing atmosphere at 1,200° C. or higher and lower than 1,415° C. in an inert gas atmosphere where an oxygen partial pressure is not more than 1,000 Pa or in a vacuum atmosphere.
In addition, the following Patent Document 2 discloses an invention of a plasma display panel (PDP), and with respect to mayenite to be used as a component of a protective layer for covering a dielectric layer of PDP, Patent Document 2 describes a method in which a raw material prepared by compounding and mixing calcium oxide (CaO) and aluminum oxide (Al2O3) in a prescribed proportion is heated to from 1,200 to 1,350° C. in air to produce a mayenite type compound by a solid phase reaction.